Arrangement for the one sided band modulation of high frequency vibrations



July 19, 1932. TRAUTWEIN 1,868,339

ARRANGEMENT FOR THE ONE-SIDED BAND MODULATION OF HIGH FREQUENCYVIBRATIONS Filed Feb. 2, 1926 o'uo'uunuun'uu'o'cu INVEHTDR Fr d lfhTmuTwein HTTOR HEY.

Patented July 19, 1932 FRIEDRICH TRAUTWEIN, F BERLIN -ZEH LEN DORE,

GERMANY, ASSIGNOR TO THE FIR-M DR. ERIGH F. HUTHGE'S. M. B. or BERLIN,GERMANY ARRANGEMENT FOR THE ONE SIDED BAND MODULATION OF HIGH FREQUENCYVIBRATIONS Application filed February 2, 1926,

It is common knowledge that in the modulation of high frequencyoscillations as a rule the amplitude is varied in a low frequency rhythmso that the average value of the high frequency amplitude fluctuates inaccordance with the low frequency. It is further known that, in thiskind of modulation, an exact and true transmission'of the low frequencyamplitude is not obtained seen from the mathematical definition of theproceeding. If the high frequency is designated-by N, the low frequencyby n, the

time by t, the high frequency amplitude by A, the low frequencyamplitude by a, and the initial amplitude designated by the index 0, amodulated oscillation has the equa- 'tion:

A=A sin Nt+A a sin [Vt sin n I This equation may be transformed into A AsinNt cos (N+ mt II composed of three frequencies, viz., the orig--inail high frequency and the sum and the difference from highand lowfrequency.

The modulation may also be explained by interference, the frequency N+nas well as the frequency N -n executing with the frequency N'a beat noteof frequency a. The ;wo beat notes assist one another in theirmutualelfect. The Equation II shows'however that, besides these twointerferences. just been mentioned, the twov which have side waves 1V+nand N 11- do also interfere,

the beat frequency of the same being equal to (N+'/1.)(1V-n)=2n, i. e.,double the originallow frequency. At the receiving station themodulation amplitude, at the surging frequency is rendered audible andis observedas sound. lVith the above described kind of modulation onehears therefore in the receiver besides the original low frequencyamplitude the octave of the same. Thereceived sounds are thereforedistorted. 'Bhisv distortion is especially disturbing if as can beeasily.

one of the two side bands.

'3. TBS 0113 1108 CLlIVG.

Serial No. 85,460, and in Germany February 3, 1925.

ance with the present state of the art of wireless telephony in order tomaintain within moderate limits the sound distortion owing'to theprominence of the octaves. The transmitter therefore normally operatesat are].- atively low degree of efiiciency.

Methods have become known to suppress It is difficult to eliminate aside-band by the usual resonance tuning method, since the breadth offrequency band obtained by modulation expressed as percentage in respectto the carrier frequency is much narrower than the technicallyobtainable minimum width of This specially holds for short waves. Evenif a'sufiiciently sharp resonance curve can be obtained, for instancewith comparatively longer waves, an unequal influence on theseveral-portions of the frequency band, i. e., distortion of the speechcurrents will be unavoidable. Filters with comparatively steep ascentare then employed.

According to'this invention the suppression of one side band is effectedby means of a compensation arrangement which is shown by way of examplein the accompanying drawing.

Fig. l is a diagrammatic representation of one embodiment of myinvention for eliminating one side band and Fig. 2 is a diagrammaticrepresentation of another embodiment of my invention wherein both thecarrier wave and one side band are eliminated. The oscillations producedby a high frequency generator 1 of any convenient type are divided insuch a manner, e. g. by properly adjusting the coupling conditions, thaton the grids of the Valves 2 and 3 similar voltage amplitudes exist. Thehigh frequency grid amplitudes in the valve 3 aredisplaced 90 in phasewith regard to those on the valve 2 by means well known in the art, thisbeing attained in Fig. 1 by the aid of the adjustable condenser 4. Thelow frequency amplitudes coming from the leading. in wire 5 areconducted to the valves 2 and 3 at voltages which are also equal regardto the-current in circuit 5 as is well .The anode currents of -p'lace inthe valve 2. The proceeding in the A =A cos N H- oscillation amplitudesupplied to the work to theantenna becomes to each other, the lowfrequency amplitude in the grid of the valve 3 being also displaced 90in phase with regard to that on the grid of valve 2. In Fig. 1 this isindicated by the connection of a voltage transformer 6 with valve 2 andvoltageotrans, former 7 with valve 3. By properly choos- 'ing thecoupling factors of the transformers the voltage drop on thecomparatively low resistance of the secondary Winding of 7 can.

be displaced 180 in phase with regard "to the inducing current of thecircuit 5, while the voltage impressed across the secondary winding of 6is displaced 90 in phase with known in the art. the valves 2 and 3 areaddedand transferred upon the'output circuit, for instance the antenna8. Instead of the ordinary "ulation shown by way of example in Fig. 1-any other kind of modulation might be used and highand low frequency maybe used in controlling the amplitude of thesignaling current. 9

grid modamplifiers -'I"o eXplain the operation it may be supposed thatthe modulation proceeding represented in the above stated Equation IItakes valve 3 is then explained by the 'following equation =A cos Nt+ Aa cos Ni cos m5 7 III which may be transformed into cos (N a )t IV Byaddition of Equations II and I'Vthe circuit, for instance Aba cos (N n)tV 7 the Equation IV would have to be subtracted from II. In'this casethe frequency N the sum N a are obtained. In bothcases I band may rice-' work circuit but only the two side present. Combining such a methodwith the combination of the modulation posite phase only the one or theother side proceedings Methods are does not occur in the bands are thecarrier wave itself method underlying this invention, the high frequencyoscillation as well as the low fre-- quency oscillation being-displaced90t-in ,3 and3 are the other pair of plitudes of the and "bands ofmodulated frequencies,fsuperimone of'the two side frequencies or'sidebands has disappeared and by similar phase or opbe supplied to a workcircuit. known for modulating a high frequency carrier wave in such amanner that" phase in one circuit with regard to the other, only oneside band will be obtained in the work circuit in an analo ous manner,without the carrier wave. In Eig. 2 such a, method is diagrammaticallyillustrated by way of example, the well-known push-pull modulation beingsupposed to be used for the suppression of the carrier wave. 1 is thehigh frequency generator, 2, and 2 are the one pair of valves for thepush-pull modulation, valves for the push-pull modulation, a phasedisplacement of 90 between the high frequency grid amtwo valves with theaid of the condenser 4; being presumed. The low frequency transformer 6serves for the modulation in the group of valves 2;, 2 from the circuit5, and the transformer 7 serves for the modulation of thegroup of valves3 3 at phase displacement of90 with regard t0 2,, 2 The modulations in22 and 3 3 free from the carrier waves, are added by common couplingat'the samerphase or at opposite phases in a work circuit, for instancethe antenna 8. Y

Iclaim: H r Y 1. A systemof modulating carrier frequency withsuppression of carrier wave and one of'the side-bands comprisingelectron device arrangements, each one connected to suppress the carrierwave, separate input circuits for said arrangements, a common outputcircuit for said arrangements, means for into two components producing a90 phase shift'between'said' components, dividing a carrier frequencywave into two components equally having a 90 phase difierencetherebetween," utilizing one component of said carrier wave and onecomponent of said modulating wave'to produce side bands of modulatedfrequencies, utilizing the remaing component of said carrier frequencyWave and the remaining component of said modulating wave to producefurther side posing resultant pairs of side bands to eliminate all but asingle side band carrier modulate-d wave and at-the same time suppressthe carrier.

r A system for producing a single side band carrier suppressed modulatedwave which comprises in combination a source of modulating waves, twocircuits branched therefrom, means in said branched circuits forproducing a phase shift in the respective branch'circuits, a source ofcarrier frequency,

'means'for deriving from said source two carrier wave components, meansfor producing a phase shift between said carrier wave rent shifted 90out of phase to balance the components, means for modulating saiddeeffect of one of the resulting modulation side rived carrier waves bythe output wave from bands in said output circuit.

said branch circuits respectively to produce upper and lower side bandsof each of said derived carrier waves, means for superimposing theresultant pairs of side bands whereby both the carrier and all but asingle side band are balanced and suppressed.

4. A system for producing a single side band carrier suppressedmodulated wave which comprises in combination a source of modulatingwaves, two circuits branched therefrom, means in said branched circuitsfor producing a phase shift in the respective branch circuits, a sourceof carrier frequency, means for deriving from said source two carrierwave components differing from each other in phase by 90, meansincluding a push-pull circuit arrangement for modulating said derivedcarrier waves by the output wave from said circuits respectively toproduce carrier suppressed upper and lower side bands of each of saidderived carrier waves, means for superimposing the resultant pairs ofside bands whereby one side band of each pair is balanced out and theremaining side bands are added.

5. A system of modulating a carrier wave with suppression of the carrierfrequency and one of the side bands comprising a pair of electron tubearrangements, each of said arrangements being connected to suppress thecarrier frequency, separate input circuits for said arrangements, acommon output circuit for said arrangements, means for producingseparate carrier frequency components and separate modulating frequencycomponents, respectively, to be applied to said arrangementsrespectively, and means for shifting the phase of one of said carrierfrequency components and one of said modulating frequency components by90 with regard to the remaining carrier frequency component and theremaining modulating frequency component respectively.

6. In a modulating system as described in claim 5 in which each of saidarrangements comprises two vacuum tubes with their grid controlled inpush-pull fashion by the respective carrier frequency component.

7 A system of modulating carrier frequency with suppression of thecarrier wave and one of the side bands comprising two electron devicearrangements including pushpull circuit connections to suppress thecarrier wave; separate input circuits for said arrangements; a commonoutput circuit for said arrangements; means for applying carriercurrents of equal frequency to said arrangements; further means forshifting the phase 90 at carrier frequency on one of said arrangements;and means for modulating both carrier currents in said arrangements inaccordance with acommon modulating cur- In testimony whereof I aflix mysignature.

DR. FRIEDRICH TRAUTWEIN.

